Fix API asymmetries with Watch variants

[joamaki]

Add *Watch variants to LowerBound, Prefix and All to make them work the same way as List and Get.

[github-actions]

$ make test
go: downloading github.com/mitchellh/mapstructure v1.5.0
go: downloading golang.org/x/term v0.16.0
go: downloading github.com/spf13/cast v1.6.0
go: downloading golang.org/x/sys v0.17.0
go: downloading github.com/fsnotify/fsnotify v1.7.0
go: downloading github.com/sagikazarmark/slog-shim v0.1.0
go: downloading github.com/spf13/afero v1.11.0
go: downloading github.com/subosito/gotenv v1.6.0
go: downloading github.com/hashicorp/hcl v1.0.0
go: downloading gopkg.in/ini.v1 v1.67.0
go: downloading github.com/magiconair/properties v1.8.7
go: downloading github.com/pelletier/go-toml/v2 v2.1.0
go: downloading golang.org/x/text v0.14.0
	github.com/cilium/statedb/reconciler/benchmark		coverage: 0.0% of statements
	github.com/cilium/statedb/reconciler/example		coverage: 0.0% of statements
ok  	github.com/cilium/statedb	5.407s	coverage: 89.0% of statements
ok  	github.com/cilium/statedb/index	0.004s	coverage: 25.5% of statements
ok  	github.com/cilium/statedb/internal	0.014s	coverage: 93.3% of statements
ok  	github.com/cilium/statedb/part	1.900s	coverage: 81.9% of statements
ok  	github.com/cilium/statedb/reconciler	2.293s	coverage: 80.8% of statements
-----
$ make bench
go test ./... -bench . -benchmem -test.run xxx
goos: linux
goarch: amd64
pkg: github.com/cilium/statedb
cpu: AMD EPYC 7763 64-Core Processor                
BenchmarkDB_WriteTxn_1-4                    	  475099	      2497 ns/op	    400423 objects/sec	    2720 B/op	      32 allocs/op
BenchmarkDB_WriteTxn_10-4                   	 1249758	       959.9 ns/op	   1041780 objects/sec	     715 B/op	      10 allocs/op
BenchmarkDB_WriteTxn_100-4                  	 1580583	       757.9 ns/op	   1319429 objects/sec	     584 B/op	       7 allocs/op
BenchmarkDB_WriteTxn_1000-4                 	 1514061	       840.0 ns/op	   1190477 objects/sec	     531 B/op	       7 allocs/op
BenchmarkDB_WriteTxn_10000-4                	 1245349	      1031 ns/op	    970327 objects/sec	     554 B/op	       7 allocs/op
BenchmarkDB_WriteTxn_100_SecondaryIndex-4   	  518604	      2259 ns/op	    442633 objects/sec	    1672 B/op	      30 allocs/op
BenchmarkDB_RandomInsert-4                  	    2440	    483108 ns/op	   2069932 objects/sec	  385862 B/op	    7097 allocs/op
BenchmarkDB_RandomReplace-4                 	     433	   2781318 ns/op	    359542 objects/sec	 1846405 B/op	   30566 allocs/op
BenchmarkDB_SequentialInsert-4              	    1550	    789985 ns/op	   1265847 objects/sec	  534136 B/op	    7288 allocs/op
BenchmarkDB_Changes_Baseline-4              	    1256	    942577 ns/op	   1060922 objects/sec	  536275 B/op	   10246 allocs/op
BenchmarkDB_Changes-4                       	     696	   1721266 ns/op	    580968 objects/sec	  964458 B/op	   14539 allocs/op
BenchmarkDB_RandomLookup-4                  	   20806	     55581 ns/op	  17991929 objects/sec	     144 B/op	       1 allocs/op
BenchmarkDB_SequentialLookup-4              	   26208	     45711 ns/op	  21876514 objects/sec	       0 B/op	       0 allocs/op
BenchmarkDB_FullIteration_All-4             	     794	   1648429 ns/op	  60663954 objects/sec	     360 B/op	       7 allocs/op
BenchmarkDB_FullIteration_Get-4             	     208	   5653215 ns/op	  17689089 objects/sec	       0 B/op	       0 allocs/op
BenchmarkDB_PropagationDelay-4              	  505299	      2231 ns/op	        19.00 50th_µs	        22.00 90th_µs	        86.00 99th_µs	    1514 B/op	      24 allocs/op
PASS
ok  	github.com/cilium/statedb	26.318s
PASS
ok  	github.com/cilium/statedb/index	0.004s
PASS
ok  	github.com/cilium/statedb/internal	0.003s
goos: linux
goarch: amd64
pkg: github.com/cilium/statedb/part
cpu: AMD EPYC 7763 64-Core Processor                
Benchmark_Insert_RootOnlyWatch-4    	    9214	    133232 ns/op	   7505712 objects/sec	  104124 B/op	    2041 allocs/op
Benchmark_Insert-4                  	    6459	    178334 ns/op	   5607470 objects/sec	  202675 B/op	    3064 allocs/op
Benchmark_Replace-4                 	29501481	        41.16 ns/op	  24295557 objects/sec	       0 B/op	       0 allocs/op
Benchmark_Replace_RootOnlyWatch-4   	29184690	        41.24 ns/op	  24248542 objects/sec	       0 B/op	       0 allocs/op
Benchmark_txn_1-4                   	 2986898	       401.7 ns/op	   2489422 objects/sec	     432 B/op	       7 allocs/op
Benchmark_txn_10-4                  	 7407723	       159.0 ns/op	   6287664 objects/sec	     152 B/op	       2 allocs/op
Benchmark_txn_100-4                 	 7381794	       171.4 ns/op	   5832763 objects/sec	     223 B/op	       2 allocs/op
Benchmark_txn_1000-4                	 7460496	       162.0 ns/op	   6174438 objects/sec	     215 B/op	       2 allocs/op
Benchmark_txn_10000-4               	 4539885	       238.3 ns/op	   4196608 objects/sec	     238 B/op	       2 allocs/op
Benchmark_txn_100000-4              	 3960884	       293.9 ns/op	   3403000 objects/sec	     340 B/op	       2 allocs/op
Benchmark_txn_delete_1-4            	 3279792	       367.3 ns/op	   2722620 objects/sec	     840 B/op	       6 allocs/op
Benchmark_txn_delete_10-4           	 8710177	       137.5 ns/op	   7271267 objects/sec	     131 B/op	       1 allocs/op
Benchmark_txn_delete_100-4          	10446565	       117.0 ns/op	   8544764 objects/sec	      60 B/op	       1 allocs/op
Benchmark_txn_delete_1000-4         	11291892	       107.0 ns/op	   9344211 objects/sec	      26 B/op	       1 allocs/op
Benchmark_txn_delete_10000-4        	 9413884	       124.5 ns/op	   8033940 objects/sec	      25 B/op	       1 allocs/op
Benchmark_txn_delete_100000-4       	 7979077	       136.8 ns/op	   7312081 objects/sec	      26 B/op	       1 allocs/op
Benchmark_Get-4                     	   38326	     32180 ns/op	  31075315 objects/sec	       0 B/op	       0 allocs/op
Benchmark_Iterate-4                 	  169270	      7364 ns/op	 135786863 objects/sec	      80 B/op	       3 allocs/op
Benchmark_Hashmap_Insert-4          	   15594	     76869 ns/op	  13009219 objects/sec	   86554 B/op	      64 allocs/op
Benchmark_Hashmap_Get_Uint64-4      	  147024	      8057 ns/op	 124110885 objects/sec	       0 B/op	       0 allocs/op
Benchmark_Hashmap_Get_Bytes-4       	  147630	      8060 ns/op	 124062391 objects/sec	       0 B/op	       0 allocs/op
Benchmark_Uint64Map_Random-4        	    1305	    920307 ns/op	   1086595 items/sec	 2685400 B/op	    9034 allocs/op
Benchmark_Uint64Map_Sequential-4    	    1394	    863628 ns/op	   1157907 items/sec	 2476394 B/op	    9749 allocs/op
PASS
ok  	github.com/cilium/statedb/part	32.635s
PASS
ok  	github.com/cilium/statedb/reconciler	0.005s
?   	github.com/cilium/statedb/reconciler/benchmark	[no test files]
?   	github.com/cilium/statedb/reconciler/example	[no test files]
go run ./reconciler/benchmark -quiet
1000000 objects reconciled in 2.74 seconds (batch size 1000)
Throughput 365148.31 objects per second
Allocated 6011410 objects, 393446kB bytes, 546576kB bytes still in use